Abstract: Objective To investigate the effect of individualized warfarin administration based on gene polymorphism on the incidence of complications after heart valve replacement in elderly patients. 
Methods Patients treated in our hospital from January to December 2019 and from January to December 2020 were selected as the research group (n=120) and another 120 patients served as the control group. The warfarin treatment plan for patients in the control group was as follows: the initial dose of warfarin was 3 mg/d, and the dose of warfarin was adjusted to 1.5-6 mg/d according to the clinical symptoms and complications of patients. After enrollment, the research group received a dose of 3 mg/d for AA type patients, 6 mg/d for GG type, and 4.5 mg/d for AG type based on the gene polymorphisms of vitamin K epoxide reductase complex subunit 1(VKORC1) and cytochrome p450 2C9 (CYP2C9). Gene polymorphism, incidence of cardiovascular events, pharmacokinetic indexes and complications were compared between the two groups. 
Results There was no significant difference in VKORC1 and CYP2C9 gene polymorphisms between the two groups (P＞0.05). International normalized ratio (INR) ［(2.01±0.02) vs. (2.22±0.01)］ (t=102.879, P＜0.001), times of excessive anticoagulation ［(9.62±2.37) vs. (22.58±2.74)］ (t=39.188, P=0.001), half-life of warfarin ［(58.71±0.02) h vs. (61.99±0.03) h］ (t=996.536, P＜0.001), and the peak time ［(2.71±0.02) h vs. (2.99±0.03) h］ (t=85.070, P=0.001) were lower in the research group than in the control group, while INR standard time ［(6.52±2.72) s vs. (4.89±2.33) s］ (t=4.986, P＜0.0.001), the clearance rate ［ (138.01±11.02) mL/h vs. (112.22±11.25) mL/h］ (t=17.940, P＜0.001), and the highest blood drug concentration ［(621.29±11.92) μg/L vs. (607.78±11.94) μg/L］ (t=8.772, P＜0.001) were higher than those in the control group. The incidence of skin purpura (χ2=4.655, P=0.031), gingival bleeding (χ2=7.211, P=0.007) and nasal bleeding (χ2=5.661, P=0.017) in the research group was lower than that in the control group. 
Conclusion The individualized administration of warfarin based on gene polymorphism can effectively reduce the incidence of complications after heart valve replacement in the elderly, and it is recommended to be popularized in clinical practice. 

Key words: heart valve prosthesis implantation, warfarin, gene polymorphism